Paul Manafort secretly met with Julian Assange three times, including once in the spring of 2016 — months before WikiLeaks released Democratic emails stolen by Russia, according to a report published Tuesday by the Guardian.

One of the alleged meetings took place around March 2016, the time Manafort began leading Donald Trump’s presidential campaign. It’s unclear what the campaign chairman and the WikiLeaks chief discussed at the Embassy in Ecuador in London, according to the Guardian, but the episode could be a key link for investigators probing possible conspiracy between the campaign and the Kremlin to sway the 2016 U.S. presidential election in Trump’s favor.

Sources told the Guardian that Manafort, who was convicted in August of eight counts stemming from special counsel Robert Mueller’s Russia inquiry, met with Assange on at least three occasions: in 2013, in 2015 and at the meeting in early 2016. That third meeting came just months before WikiLeaks released a trove of politically damaging Hillary Clinton and Democratic Party emails that had been stolen by Russia.

The meeting lasted about 40 minutes, according to the Guardian.

Mueller’s investigators have been examining communications between the Trump campaign and WikiLeaks as part of the FBI’s Russia probe.

Donald Trump Jr., the president’s eldest son, has confirmed he communicated with the organization, and Roger Stone, a confidant of the president, reportedly told associates that Assange had briefed him on the stolen documents before their release to the public.

During the presidential campaign, Trump repeatedlycitedWikiLeaks, and infamously said “I love WikiLeaks!” during a campaign stop weeks ahead of Election Day.

WikiLeaks is seen by U.S. intelligence officials, including Trump allies like Secretary of State Mike Pompeo, as “a nonstate hostile intelligence service, often abetted by state actors like Russia.”

Mueller seemed to allude to the organization in an indictment in July charging Russian intelligence officers over Moscow’s 2016 election interference. The special counsel alleged that Guccifer 2.0 — an online persona used by Russian intelligence — released some of the stolen documents through a “website ... that had previously posted documents stolen from U.S. persons, entities and the U.S. government.”

Assange, who has lived at the Ecuadorian Embassy in London since 2012, after being accused of rape, has reportedly been charged under seal in the United States. He has been under U.S. investigation since 2010, when Chelsea Manning provided classified government documents to WikiLeaks.

The report that Manafort met with the WikiLeaks founder came a day after Mueller accused the ex-Trump campaign chairman of breaching the cooperation agreement he signed to avoid a second trial, which had been scheduled for September. The special counsel alleged in a filing Monday that Manafort lied to investigators after signing a plea deal.

Both WikiLeaks and Manafort strongly denied the meeting and threatened legal action against the Guardian over the story, which the former Trump campaign chairman described as “deliberately libelous.”